As disclosed in JP-A-2001-90700, a jet pump jets fluid to generate negative pressure, so that the fluid is drawn into a fluid inlet by the negative pressure.
In the structure disclosed in JP-A-2001-90700, a gap is formed between a jet nozzle and the fluid inlet of the sub-tank. The outer circumferential periphery of the gap is entirely opened, so that the opening area of the gap is widened. The jet pump generates negative pressure, so that fluid is drawn through the gap. Thereby, a large amount of fluid can be introduced into the fluid inlet. The structure disclosed in JP-A-2001-90700 may be applied to a fuel feed apparatus that introduces fuel into a sub-tank received in a fuel tank using a jet pump. In this case, a predetermined amount of fuel can be drawn into the sub-tank, so that a predetermined degree of the pump head can be secured in the sub-tank. The pump head is equivalent to the fuel level in the sub-tank.
However, in the structure disclosed in JP-A-2001-90700, the gap formed between the jet nozzle and the fluid inlet (fuel inlet) of the sub-tank is entirely opened at the outer circumferential periphery. Accordingly, when the fuel level decreases in the fuel tank, fuel on the side of the upper surface is drawn into the fuel inlet by negative pressure, and vortex is caused between the fuel surface and the jet nozzle. As a result, air is drawn into the fuel inlet due to vortex, and pumping noise may arise, even when the fuel level is relatively high in the fuel tank.
According to JP-A-2001-132568, the gap formed between the jet nozzle and the fuel inlet of the sub-tank is covered with a covering member on the side of the surface of fuel. Thereby, vortex is restricted from arising between the jet nozzle and the surface of fuel, so that pumping noise is reduced. The covering member is opened on the bottom side thereof, i.e., on the opposite side of the surface of fuel. Thereby, the opening formed in the bottom of the covering member is located in the vicinity of both the jet nozzle and the fuel inlet of the sub-tank, so that fuel can be easily introduced into the sub-tank.
Here, when fuel remaining in the fuel tank decreases, and the fuel level becomes lower than a dead storage level, fuel cannot be fed into the sub-tank by the jet pump. In the structure disclosed in JP-A-2001-132568, pumping noise is reduced, and an amount of fuel introduced into the sub-tank is maintained, however, the dead storage level is not considered.
Here, when fuel remaining in the fuel tank decreases, and the fuel level becomes lower than a pumping noise arising level, pumping noise becomes large. As the covering member extends to the bottom side, the pumping noise arising level is lowered. That is, when the covering member extends to the bottom side, fuel in the fuel tank can be drawn without arising large pumping noise, even when the fuel level is low. On the contrary, as the covering member extends to the bottom side, the area of the opening, through which fuel is drawn, becomes small, and the pump head decreases.
As shown in FIGS. 12, 13, a gap 320 is formed between a fuel inlet pipe 302, through which fuel is introduced from a sub-tank 300, and a jet nozzle 312 of a jet pump 310. The opening 320 is covered with a covering member 314 similarly to the structure in JP-A-2001-132568. When the gap 320, through which furl is drawn, is small, fuel filling the gap 320 may be frozen in a low temperature condition. When the distance between the jet nozzle 312 and the fuel inlet pipe 302 is increased, fuel filling the gap 320 is not apt to be frozen, however, an amount of fuel introduced into the sub-tank 300 decreases. When the opening area of the gap 320 is small, fuel cannot be drawn into the sub-tank 300 by a predetermined amount, and the pump head decreases.